Compared with traditional communication patterns, using video conference system can not only improve the work efficiency, but also free the participants from long traveling, and even it can satisfy the need for dealing with emergencies and multi-party communications and coordination. Therefore, it is a conference pattern of cost-saving, time-saving and high efficiency. With the development of large domestic enterprises and multinational company groups, and with the increase of mobility of people's work and study, the demand of enterprises and individual for video communications is increasing; therefore, the demand for video conference to operation is increasing.
Multipoint control unit, also known as multipoint conference controller, is called MCU. MCU, the function of which is similar to that of a switchboard, is the key equipment of multi-point video conference system. After synchronously separating the information flow from each conference sites, it extracts information and signaling, such as audio, video, data and the like, then sends the information and signaling of respective conference sites to a same processing module to carry out corresponding processes, such as mix and switch of the audio, mix and switch of the video, data broadcasting and routing selection, timing and conference controlling, and the like, and at last, recombines various kinds of information needed by respective conference sites, and then sends them to corresponding terminal equipments and systems.
H.323 is a standard protocol stack of International Telecom Union (ITU). The protocol stack is an organic whole and the protocols in the protocol stack can be classified into four types according to their functions. That is, the protocol stack has made comparatively detailed provisions in various aspects, such as the overall framework of the system (H.323), video codec (H.263), audio codec (H.723.1), system control (H.245), data flow multiplexing (H.225), and the like.
After the video conference comes into operation, currently, the signaling portion is using only one H.323 protocol stack for one MCU, and the signaling interaction processes of H.225 and H.245 in the call process are all carried out by the protocol stack. There is a great amount of signaling which need to be processed by protocol stack in large capacity calls. If the H.225 and H.245 signaling are both processed on one protocol stack, due to the limitation of hardware, problems that the signaling can not be processed timely will occur, which will cause the situations of hung up due to signaling replying overtime and signaling lost, and thus, obviously, the processing efficiency of this method is not high. Therefore, the number of processable calls of one MCU is limited. As the number of users of a video conference operation system increases, the largest number of calls that can be accommodated by one MCU will become a bottleneck.
Thus, the problem of how to implement large capacity calls by using H.323 protocol stack should be taken into consideration by those skilled people.